1. Field of the Invention
The present invention relates to an image recording device arranged to conduct a recording process for an image forming apparatus such as a copier, a facsimile machine, a printer and a multifunction peripheral, particularly, to technology used to adjust a pressing force of a developing roller against a photoconductive drum.
2. Description of the Related Art
One of the substantive problems found in these image recording devices is deterioration in the image quality of a recorded image, which deterioration is caused by such change as making a pressing force of a developing roller large or small against a photoconductive drum. That is, aging and the like changes a biasing force of an elastic member arranged to press a developing roller against a photoconductive drum so that the previously-mentioned pressing force may be changed to deteriorate, the image quality of the recorded image. In addition, also in a case where developing rollers have variations in their diameters, the pressing force may change.
This problem becomes apparent in a case where a developing roller is replaceably configured. That is, this problem becomes apparent in a configuration where a toner agitating member and a developing roller are integrated as a developing unit so that the developing unit is replaced to replace the developing roller. This is because, in addition to such a factor as a change of biasing force of an elastic member variation in a structure for mounting a developing unit on a photoconductive unit, there is also a factor for changing the pressing force. In particular, a configuration in which developing unit is configured to be removably/rotatably mounted onto a coupling axis arranged between the photoconductive unit and the developing unit, worsened by complicated mounting structure, easily changes the pressing force when the developing unit is replaced.
Therefore, for example, an image forming apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2011-102908 arranges a pressing unit arranged to press a developing unit against a photoconductive unit in a developing-device-housing unit arranged therein. That is, Japanese Unexamined Patent Application Publication No. 2011-102908 discloses a configuration arranged to press a developing unit against a photoconductive unit by using a pressing unit in an image forming apparatus which configures the developing unit to be removably and rotatably mounted on a coupling axis arranged between the photoconductive unit and the developing unit as described above. The pressing unit includes a cylindrical member, an elastic member arranged in the cylindrical member, and a movable member arranged to be moved in the cylindrical member by receiving a biasing force of the elastic member. By pressing the developing unit against the photoconductive unit by the biasing force of the elastic member, the developing roller can be arranged at a more precise position against the photoconductive drum.
However, the pressing unit according to Japanese Unexamined Patent Application Publication No. 2011-102908 cannot adjust the pressing force of the developing roller against the photoconductive drum at all. Consequently, in a case where the biasing force of the elastic member is changed or where the dimensions of the developing rollers are different, as mentioned above, the developing roller cannot be pressed against the photoconductive drum with an appropriate pressing force so that the image quality of the recorded image may deteriorate.